Optically variable element comprising a sequence of thin-film layers

ABSTRACT

The invention concerns an optically variable element, in particular an optically variable safeguard element for safeguarding banknotes, credit cards and the like, and a security product and a foil, in particular an embossing foil or a laminating foil, with such an optically variable element. The optically variable element has a thin film layer ( 54, 55, 58 ) for producing color change by means of interference and a further layer ( 51, 52, 53, 59 ). The thin film is in the form of a partial thin film element which covers the surface region of the further layer only in region-wise and pattern-shaped manner.

The invention concerns an optically variable element, in particular anoptically variable security element for safeguarding banknotes, creditcards and the like, which has a thin film for producing color shifts bymeans of interference. The invention further concerns a security productand a foil, in particular an embossing foil or a laminating foil, whichhas such an optically variable element.

Optically variable elements are frequently used to make it difficult tocopy and misuse documents or products and if possible to prevent thatfrom happening. Optically variable elements are frequently used forsafeguarding documents, banknotes, credit cards, cash cards and thelike.

In order to make it difficult to copy optically variable elements, it isknown for an optically variable element to be provided with a thin filmlayer succession which produces color shifts by means of interference,in dependence on the viewing angle.

WO 01/03945 A1 describes a security product having a transparentsubstrate, to one side of which is applied a thin film which produces aperceptible color shift in dependence on the change in the angle ofview. The thin film comprises an absorption layer which is applied tothe transparent substrate and a dielectric layer which is applied to theabsorption layer. The absorption layer includes a material which is madeup from one of the following materials or a combination of thosematerials: chromium, nickel, palladium, titanium, cobalt, iron,tungsten, molybdenum, iron oxide or carbon. The dielectric layercomprises one of the following materials or a combination of thefollowing materials: silicon oxide, aluminum oxide, magnesium fluoride,aluminum fluoride, barium fluoride, calcium fluoride or lithiumfluoride.

In order further to increase the level of safeguard against copying, adiffraction pattern is embossed on the side of the transparentsubstrate, which is in opposite relationship to the thin film layersuccession. That diffraction pattern acts as a diffraction grating sothat for example the illusion of a three-dimensional image can beproduced for the viewer, by means of that two-dimensional pattern.

It is further proposed that the diffractive pattern be applied byembossing to the side of the transparent substrate to which the thinfilm layers are also applied.

Those two embodiments of an optically variable element provide that, ateach location of the optically variable element, the optical effectsproduced by the thin film layers and the optical effects produced by thediffractive pattern are superimposed and this therefore overall affordsan optical effect which is difficult to imitate and copy.

The invention is now based on an optically variable element as isdescribed in WO 02/00445 A1.

The optically variable element comprises here a plurality of layerswhich are arranged generally in mutually superposed relationship. Theoptically variable element has on the one hand a thin film whichproduces the optical effect, already described above, of a color changewhich is dependent on the angle of view. In addition the opticallyvariable element has a replication layer into which a relief structureis embossed. That relief structure produces a further optical effect,namely the diffraction effect which has already been describedhereinbefore and by means of which holograms and the like can berepresented. In that respect, in regard to production procedure, firstlythe thin film layers are applied to the replication layer and then therelief structure is embossed thereon.

As an alternative thereto, WO 02/00445 A1 describes that the opticaleffect produced by the thin film structure and the optical effectproduced by the relief structure are decoupled from each other. Twooperating procedures are proposed for that purpose.

On the one hand it is proposed that an opaque layer is applied betweenthe relief structure which produces a holographic image by means ofdiffraction and the thin film which produces a color change effect. Therelief structure is screened from the thin film structure by means ofthat opaque layer. The second possible option involves arranging two ormore layers of a substantially transparent material between the reliefstructure producing a holographic image by diffraction and the thin filmlayers. Those layers can include one or more highly refractive layersand an adhesive layer. Those layers provide for an increase inreflection and thus the strength of light in the region of the reliefstructure producing a holographic image.

In this respect, such a variable optical element can be produced asfollows: firstly a pattern is embossed into a holographic foil. Thatfoil is then provided in region-wise manner with a metal layer. The thinfilm layers are then vapor-deposited in succession. Lastly, a metallayer is applied, over the full surface area.

A further possible option involves providing a prefabricated thin filmlayer succession with an embossable lacquer and then embossing therelief structure into that lacquer. It is further proposed that suchprefabricated thin film layers can be glued to prefabricatedmicrostructures.

WO 02/00445 A1 thus describes either using security elements in whichthe optical effect produced by diffractive structures and the opticaleffect produced by thin film structures are coupled together, or usingsecurity elements in which the optical effect produced by diffractivestructures and the optical effect produced by thin film layers aredecoupled from each other.

Now, the object of the invention is to make it difficult to imitate andcopy optically variable elements and thus to improve the anti-forgerysecurity of security products.

That object is attained by an optically variable element, in particularan optically variable safeguard element for safeguarding banknotes,credit cards and the like, which has a thin film for producing colorshifts by means of interference and a further layer, wherein the thinfilm is in the form of a partial thin film element which covers thesurface region of the further layer only in region-wise andpattern-shaped manner. That object is further attained by a securityproduct and a foil, in particular an embossing foil or a laminatingfoil, which has such an optically variable element.

The invention achieves the advantage that an optically variable elementaccording to the invention is substantially more difficult to copy thanthe optically variable elements known in the state of the art. As aresult, the anti-forgery security of security products provided with anoptically variable element of the configuration according to theinvention is considerably increased. In particular the level ofanti-forgery security is far increased in that respect in comparisonwith surface elements of a sandwich-like structure.

Thus for example the optically variable element described in WO 02/00445A1—as described in WO 02/00445 A1 as a possible mode of manufacture—canbe imitated by a prefabricated thin film foil being processed with anembossing stamp, with which a diffractive structure is embossed into thethin film foil. That is no longer possible with an optically variableelement designed in accordance with the invention: the partialapplication of a thin film layer succession which produces a color shiftby means of interference requires a high level of technologycomplication and expenditure. In comparison with a prefabricated thinfilm foil the partial thin film element produced in that way representsan individualised element so that imitation of the optically variableelement is no longer possible, starting from a prefabricated thin filmlayer succession.

Further advantages in relation to previous individual representations ormutually superposed surface elements lie in better optical integrationinto the overall element to be protected, the specifically targetedgeometrical arrangement of functional windows (machine-readability,personal data and so forth) and the choice, which can be better matched,in respect of the physical-chemical properties of the partially arrangedindividual elements (corrosion, intermediate layer adhesion and thelike).

Advantageous configurations of the invention are set forth in theappendant claims.

The further layer is preferably a continuous protective lacquer layer, acontinuous reflection layer or a continuous adhesive layer. There ishowever no need for the further layer to cover the entire surface regionof the optically variable element. Besides the further layer, it ispossible to provide additional further layers whose surface regions arecovered by the partial thin film element only in region-wise andpattern-shaped manner. For example it is thus possible for the opticallyvariable element to have a continuous protective lacquer layer, acontinuous reflection layer and a continuous adhesive layer.

It is desirable for the partial thin film element to be made up of anabsorption layer and a spacer layer. It is further possible for thepartial thin film element to be made up from a relatively large numberof layers which have alternately different refractive indices.

The level of anti-forgery security can be further increased by thepartial thin film layer having a reflective layer, preferably a metallayer. That improves the recognisability of the partial thin filmelement.

Alternatively there is also the possibility of providing the partialthin film element with a transmission layer. In that case it isparticularly advantageous for that transmission layer to be colored andthus to provide an additional security feature.

It is further possible to provide the partial thin film element with adiffractive structure, as an additional security element. Such adiffractive structure makes it possible to produce for examplediffraction effects, by means of which for example holograms or definedcolor effects can be produced.

Imitation of the optically variable element can be made still moredifficult if the partial thin film element is provided with a partialreflective layer, in particular a metal layer, which only partiallycovers the surface region of the partial thin film element. Besides theincrease in the level of anti-forgery security that this entails, thatalso makes it possible to achieve attractive decorative effects. Thattherefore increases the array of shapes available for the designconfiguration of an optically variable element.

These advantages can be achieved by the partial thin film element beingprovided with a partial diffractive structure which only partiallycovers the surface region of the partial thin film element.

Those two measures, namely the partial reflective layer and the partialdiffractive layer, can also be embodied in parallel.

A possible way, which enjoys production-engineering advantages, ofdesigning a surface region, which is delimited by the partial thin filmelement, of the optically variable element, involves applying anabsorption layer but no spacer layer in that surface region. Thoseadvantages are further also achieved in that a spacer layer but not anabsorption layer is applied in the surface region of the opticallyvariable element which is delimited by the partial thin film element.

There is also the possibility of applying one or more substitute layers,in a surface region, which is delimited by the partial thin filmelement, of the optically variable element, said one or more substitutelayers replacing the thin film of the partial thin film element in thatsurface region. Preferably, that surface region which is delimited bythe partial thin film element is enclosed by the partial thin filmelement or encloses the thin film element. That measure makesparticularly high demands on the production process. Accordingly,imitation of an optically variable element of such a configuration ismade more difficult and thus the level of anti-forgery security isimproved.

Advantages in regard to the following layer structure can be afforded ifthe overall layer thickness of the one or more substitute layersapproximately corresponds to the layer thickness of the partial thinfilm element.

Imitation of the optically variable element can be further made moredifficult if one of the one or more substitute layers is provided with adiffractive structure. That advantage is further achieved by applying,as the substitute layers, a reflection layer and a carrier layer.Alternatively it is also possible to apply a single substitute layerwhich for example involves a reflection layer. As described hereinafter,such a procedure can enjoy advantages from the point of view ofproduction engineering.

As already discussed in relation to the partial thin film element, it isalso advantageous, in regard to the configuration of the one or moresubstitute layers, for those layers to have a partially reflective layerwhich only partially covers the surface region of the one or moresubstitute layers. In that way, besides the resulting enhancement in thedegree of anti-forgery security, it is also possible to achieveintegrating attractive decorative effects for the security product. Thearray of shapes available for the design configuration of an opticallyvariable element is enhanced in that way. Those advantages can furtherbe achieved if the one or more substitute layers have a partialdiffractive structure which only partially covers the surface region ofthe one or more substitute layers.

It is possible for the configurational elements ‘partial thin filmelement with partial reflective layer’, ‘partial thin film element withpartial diffractive structure’, ‘substitute layer with partialreflective layer’, and ‘substitute layer with partial diffractivestructure’ to be combined together as desired. An optically variableelement according to the invention can thus have a plurality ofcombinations of valuable security features and affords a large number ofattractive configurational features.

The invention is described hereinafter by way of example by means of anumber of embodiments with reference to the accompanying drawings inwhich:

FIG. 1 shows a view in section through an optically variable element,

FIG. 2 a shows a view of an optically variable element according to theinvention, in a first embodiment,

FIG. 2 b shows a view of an optically variable element according to theinvention, in a second embodiment,

FIG. 2 c shows a view of an optically variable element according to theinvention, in a third embodiment,

FIG. 3 shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 4 shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 5 a shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 5 b shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 5 c shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 6 a shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 6 b shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,

FIG. 7 shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention,and

FIG. 8 shows a view in section through an optically variable elementaccording to the invention for a further embodiment of the invention.

FIG. 1 shows the structure in principle of an optically variable element0.

The optically variable element 0 is intended to be applied to a securityproduct, for example a banknote, a credit card, a cash card or adocument. There is also the possibility that the optically variableelement is intended to be applied as a security or authenticityidentification to an article, for example to a CD, or to a packaging.

The optically variable element 0 can assume many different forms. Theoptically variable element 0 can thus be for example a security threadwhich is intended to be applied to one of the above-specified objects.

FIG. 1 shows a carrier 1 and five layers 2 through 6. The opticallyvariable element 0 is formed by the layers 2 through 6. The layer 2 is aprotective lacquer and/or release layer, the layer 3 is an absorptionlayer, and the layer 4 is a spacer layer. The layer 5 is a metal layeror an HRI layer (HRI=High Refractive Index). The layer 6 is an adhesivelayer.

The carrier 1 comprises for example PET. The carrier serves forproducing the optically variable element, from theproduction-engineering point of view. Upon or after application of theoptically variable element to the object to be safeguarded, the carrier1 is removed. FIG. 1 therefore shows the optically variable element at astage in which it is part of a foil, for example an embossing foil or alaminating foil.

In the case where the optically variable element 0 is part of alaminating foil, the layer 2 has a bonding layer.

In principle, a thin film is distinguished by an interference layerstructure which produces color shifts which are dependent on the viewingangle. It can be in the form of a reflective element, with for examplehighly reflective metal layers, or in the form of a transmissive elementwith a transparent optical separation layer of higher refractive index(HRI) or lower refractive index (LRI), in relation to the adjoininglayers. The base structure of the thin film has an absorption layer(preferably with between 30% and 65% transmission), a transparent spacerlayer as a color change-producing layer (for example λ-quarter or λ-halflayer) and a metal layer as a reflective or an optical separation layeras a transmitting layer.

The layers 3, 4 and 5, that is to say the absorption layer, the spacerlayer and the metal layer or HRI layer form a thin film which producescolor shifts dependent on the viewing angle, by means of interference.In that respect, the color shifts produced by the thin film arepreferably in the range of the light which is visible to a human viewer.In addition that thin film is in the form of a partial thin film elementwhich covers the surface region of the optically variable element 0 onlyin a region-wise and pattern-shaped manner.

If the layer 5 comprises a reflective layer, for example aluminum, thenthe layer thickness of the spacer layer 4 is to be so selected that theλ/4 condition is satisfied. If the layer 5 comprises a transmissivelayer then the spacer layer 4 has to satisfy the λ/2 condition.

It is possible for the partial thin film element to be made up of asuccession of high-refractive and low-refractive layers. For example thepartial thin film element can be made up of between 3 and 9 such layers(odd number of thin film layers) or between 2 and 10 such layers (evennumber of thin film layers). The higher the number of layers, the moresharply can the wavelength be set for the color change effect.

Examples of usual layer thicknesses for the individual layers of thepartial thin film element and examples of materials which can be used inprinciple for the layers of the partial thin film element are disclosedin WO 01/03945, page 5, line 30 through page 8, line 5.

The layer 5 can be in the form of a full-area or a partial metal layeror an HRI layer. The materials for the layer 5 can be for example Al,Ag, Cr, Ni, Cu, Au or combinations of reflective metals.

It is further possible for the layer 5 to have a structured surface.Thus it can have a diffractive structure, a refractive structure(lenses) or macroscopic structures (greater than 30 μm). It can furtheralso have an unstructured, mirror-reflecting or scattering surface.

It is possible in principle to forego one or more of the layers shown inFIG. 1. In addition the optically variable element 0 can also have oneor more further layers.

FIGS. 2 a through 2 c show three optically variable elements 10, 20 and30 respectively. The optically variable element 10 has three surfaceregions 11 through 13, the optically variable element 20 has threesurface regions 21 through 23 and the optically variable element 30 hasthree surface regions 31 through 33.

The surface regions 12, 23 and 31 of the optically variable elements 10,20 and 30 are each covered by a respective partial thin film element. Ascan be seen from FIGS. 2 a through 2 c, the partial thin film element isformed in each case in a region-wise and pattern-shaped manner.

It is possible in this case for the respective partial thin film elementto be of a transmissive or reflective nature. A partial, pattern-shaped,both transmissive and also reflective configuration within therespective surface region makes it possible to achieve furtherattractive effects. In addition the surface regions 12, 23 and 31 canalso be provided with a diffractive structure.

The surface regions 11, 22 and 33 of the optically variable elements 10,20 and 30 respectively are each covered with a partial metallisation.Those surface regions can also be provided with a diffractive structure.

A respective transparent window is visible in each of the surfaceregions 13, 21 and 32 of the optically variable elements 10, 20 and 30.The transparent windows each have a partial transparent element. Thatelement has transparent or transmissive properties (clear lacquercompositions, oxidic, partially metallised, scattering, transmissive,organic and inorganic compositions). Those surface regions can also beprovided with a diffractive structure.

It is to be emphasised that the diagrammatically illustrated elementarrangements of FIGS. 2 a through 2 c can all be embodied in registerrelationship with each other and without limitation in terms ofgenerality, can embrace both graphic image elements, alphanumeric andgeometric characters, bar codes and random patterns and combinationsthereof.

FIG. 3 shows a possible way of constructing an optically variableelement which is provided with a partial thin film element.

FIG. 3 shows a carrier 31, five layers 32 through 37 and two surfaceregions 39 a and 39 b.

The layer 32 is a protective lacquer and/or release layer, while thelayer 33 is a replication layer formed for example by a replicationlacquer. The layer 35 is a metal layer or an HRI layer (HRI=HighRefraction Index). The layer 36 is formed by an etching resist. Thelayer 37 is an adhesive layer.

To produce the layer structure, the protective lacquer and release layer32, the replication layer 33 and the metal layer 35 are applied to thecarrier 31 over the full surface area involved. Then the layer 35 ispartially provided with diffractive structures by means of an embossingtool. The metal layer 35 is then printed upon with an etching resist, sothat the only partially shaped layer 36 is formed.

The area which is not covered by the etching resist is then removed byetching.

Alternatively, it is also possible for the metal layer 5 to bedemetallised or removed by ablation processes such as laser ablation,spark erosion, plasma or ion bombardment. It is possible by means ofsuch ablation processes to transfer digitally stored images, texts andcodes.

A partial thin film element is now introduced into the intermediatespaces formed in that way between the partial layers 35 and 36. In thiscase, the layers of the partial thin film element can be applied byvapor deposition with suitably shaped vapor deposition masks or byprinting on the layers, in the region of the intermediate spaces.

It is further possible that, as shown in FIG. 3, partial regions of theintermediate spaces are not covered by the partial thin film element andthat therefore affords a transparent window. When the adhesive layer isapplied the adhesive layer is of a correspondingly thicker configurationat those locations, as shown in FIG. 3.

FIG. 4 shows an optically variable element in which a surface regiondelimited by a partial thin film element, of the optically variableelement has a spacer layer but not an absorption layer.

FIG. 4 shows a carrier 41, five layers 42 through 47 and a plurality ofsurface regions 49 a and 49 b.

The layer 42 is a protective lacquer and/or release layer, and the layer43 is an absorption layer. The layer 44 is a spacer layer. The layer 46is a metal layer or an HRI layer (HRI=High Refraction Index). The layer47 is an adhesive layer.

To produce that layer structure, the protective lacquer and releaselayer 42 and the absorption layer 43 are applied to the carrier 41 overthe full surface area involved. In this case the absorption layer 43 canbe applied by vapor deposition or by a printing process.

The absorption layer is then partially removed in the surface regions 49b.

That partial removal of the absorption layer is effected by positiveetching or negative etching. Thus, in the case of direct etching, anetching agent can be applied in the form of a pattern by a printingprocess, for example by means of a roller or by screen printing. It isalso possible to apply an etching mask which is removed by a washingoperation after the etching process.

It is further possible for the absorption layer to be removed by anablation process such as laser ablation, spark erosion, plasma or ionbombardment. By means of such ablation processes it is possible totransfer digitally stored images, texts and codes.

Instead of the absorption layer being applied over the full surfacearea, it is also possible for the absorption layer to be applied onlypartially to the layer 42. That can be effected by vapor deposition bymeans of vapor deposition masks of a pattern configuration or bycorrespondingly pattern-shaped printing of the absorption layer 43 onthe layer 42.

The spacer layer 44 is now applied over the full surface area involved,to the partially shaped absorption layer 43. The operation of applyingthe spacer layer can be effected for example by vapor deposition or byprinting the absorption layer over the full surface area involved.

After that procedure the surface regions 49 a are covered with a thinfilm comprising the absorption layer 43 and the spacer layer 44. Thatthin film (after application of the further layers which act as opticalseparation layers) produces color shifts which are dependent on theviewing angle, by means of interference, upon suitable incidence oflight. The absorption layer 43 is not present in the surface regions 49b so that such color shifts cannot be produced there.

It is further possible for not only the absorption layer 43 but also thespacer layer 44 to be only partially applied to the absorption layer 43or partially removed.

There is on the one hand the possibility of applying the spacer layer 44to the partially shaped absorption layer 43 over the full surface areainvolved and then removing the spacer layer by one of theabove-described processes (positive etching, negative etching, ablation)in register relationship with the partially shaped absorption layer.

There is also the possibility of applying the absorption layer 43 andthe spacer layer 44 over the full surface area and then removing bothlayers jointly by one of the above-described processes (positiveetching, negative etching, ablation).

There is also the possibility of printing on the spacer layer inregister relationship with the partially shaped absorption layer, bymeans of a printing process.

Alternatively it is also possible for the surface regions, which aredelimited by the partial thin film element, of the optically variableelement to have an absorption layer but no spacer layer.

That can be achieved if the absorption layer is applied over the fullsurface area, for example by vapor deposition or printing. The spacerlayer is then only partially applied by a printing process. Here toothere is the possibility of the spacer layer being applied over the fullsurface area and then removed by one of the above-described processes(positive etching, negative etching, ablation).

There is also the possibility of the spacer layer or the absorptionlayer being altered in respect of its thickness by over-vapor depositionor over-printing, in such a way that it can no longer perform itsfunction as an interference layer and is thus ‘extinguished’.

The layer 46 is now applied to the layers 43 and 44 which have beenapplied and configured in the above-indicated fashion.

If the layer 46 is a reflection layer it preferably comprises a metal.That metal can also be colored. The materials that can be used areessentially chromium, aluminum, copper, iron, nickel, silver, gold or analloy with those materials.

It is further possible in that case to apply highly shiny or reflectivemetal pigments which then form the reflection layer.

It is further possible for the layer 46 to be in the form of a partialmetal layer. Here too there is the possibility that the layer 46 isfirst applied over the full surface area, for example by vapordeposition, and then removed by one of the above-described processes(positive etching, negative etching, ablation). If metal pigments areused as the reflective layer, that layer can be partially printed on,thereby then producing a partial reflective layer.

If the layer 46 is in the form of a transmission layer, in particularmaterials such as oxides, sulfides or chalcogenides can be used asmaterials for that layer. The crucial consideration in regard to thechoice of the materials is that there is a difference in refractiveindex, in relation to the materials used in the spacer layer 44. Thatdifference should be not less than 0.2. Depending on the respectivematerial used for the spacer layer 44, an HRI material or an LRImaterial is thus used for the layer 46. In this case the transmissionlayer can also be formed by an adhesive layer which satisfies thatcondition in regard to refractive index.

An ‘extinguishing effect’ as described hereinbefore can further beachieved by partial application of the transmission layer. If the spacerlayer is adjoined by a layer (for example an adhesive layer) which doesnot satisfy the above-described condition in regard to refractive index,the optical thickness of the spacer layer is increased and the visibleinterference effect no longer occurs.

Reference is now made to FIGS. 5 a through 5 c to describe possible waysof applying one or more substitute layers which are provided with adiffractive structure, in the surface region of the optically variableelement, which surface region is delimited by a partial thin filmelement.

FIG. 5 a shows a carrier 51, eight layers 52 through 59 and a pluralityof surface regions 59 a and 59 b. The layer 52 is a protective lacquerand/or release layer. The layer 53 is a replication layer. The layer 54is an absorption layer. The layers 56 and 57 are substitute layers. Thelayer 58 is a metal layer or an HRI layer (HRI=High Refraction Index).The layer 59 is an adhesive layer.

The layers 52, 53, 54, 55, 58 and 59 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 51 as described there.

The layer 53 comprises a replication lacquer or a thermally shapableplastic material. Diffractive structures are now embossed into the layer53 in the surface regions between the partial thin film layer. Thatembossing operation is advantageously carried out before the layers 54and 55 are applied.

Instead of an embossing operation the diffractive structure can also beapplied to the surface of the layer 53 by means of a laser.

The layer 57 which is preferably a metal layer is then applied in thesurface regions 59 b.

In this case, that metallisation can be applied by vapor depositionusing a mask prior to or after forming the partial thin film element.

It is further possible for metallisation over the full surface area tobe applied to the layer 53, and for that metallisation to be removed bymeans of one of the above-described processes (positive etching,negative etching, ablation) partially in the surface regions 59 a, thatis to say in the region of the partial thin film element. In this casethat step is effected before the partial thin film element is produced.

The embossing operation can also be effected only after the layer 57 hasbeen applied.

The substitute layer 56 can comprise the same material as the spacerlayer 55, which has the advantage that it is possible to foregopartially applying the spacer layer 55 and the substitute layer 56.

FIG. 5 b shows a carrier 61, eight layers 62 through 69 and a pluralityof surface regions 69 a and 69 b. The layer 62 is a protective lacquerand/or release layer. The layer 63 is a replication layer. The layer 64is an absorption layer. The layers 66 and 67 are substitute layers. Thelayer 58 is a metal layer or an HRI layer (HRI=High Refraction Index).The layer 59 is an adhesive layer.

The layers 62, 63, 64, 65, 68 and 69 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 61 as described therein.

The layer 63 comprises a replication lacquer or a thermally shapableplastic material. The layer 63 is provided with a diffractive structureand in the surface regions 69 a with the layer 67, as described in thedescription relating to FIG. 5 a.

In contrast to the embodiment illustrated in FIG. 5 a the layer 68 is ofan only partial nature. That can be achieved by partial application ofthe layer 68, effected as described hereinbefore. It is further possiblethat, upon vapor deposition of the layer 68, the layer 67 is alsoproduced by vapor deposition in parallel, and then the layer 66 ispartially applied. The layer 66 however can also be part of the adhesivelayer 69 (see also the description relating to FIG. 3).

FIG. 5 c shows a carrier 71, eight layers 72 through 79 and a pluralityof surface regions 79 a and 79 b. The layer 72 is a protective lacquerand/or release layer. The layer 73 is a replication layer. The layer 74is an absorption layer. The layers 76 and 77 are substitute layers. Thelayer 78 is a metal layer or an HRI layer (HRI=High Refraction Index).The layer 79 is an adhesive layer.

The layers 72, 73, 74, 75, 78 and 79 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 71 as described therein.

The layer 73 comprises a replication lacquer or a thermally shapableplastic material. The layer 73 is provided with a diffractive structureand in the surface regions 79 a with the layer 77, as described in thedescription relating to FIG. 5 a.

In contrast to the embodiments illustrated in FIGS. 5 a and 5 b thelayers 77 and 76 are both metal layers. Thus for example the metal layer77 is applied as described with reference to FIG. 5 a, and provided witha diffractive structure. By virtue of a clever choice of the materialfor the spacer layer 75, it is possible to provide that it has metallicproperties in the surface regions 79 b. The metal layer 79 is thenapplied over the full surface area.

It will be appreciated that it is also possible for the layers 77 and 76to be applied as a single metal layer, just with the greater layerthickness which can be seen from FIG. 5 c, as described in thedescription relating to FIG. 5 a.

Reference is now made to FIGS. 6 a and 6 b to describe possible ways inwhich one or more transparent substitute layers can be provided in thesurface region of the optically variable element, which surface regionis delimited by a partial thin film element.

FIG. 6 a shows a carrier 81, seven layers 82 through 89 and a pluralityof surface regions 89 a and 89 b. The layer 82 is a protective lacquerand/or release layer. The layer 83 is a replication layer. It would alsobe possible in this case to forego that layer. The layer 84 is anabsorption layer. The layer 86 is a substitute layer. The layer 88 is ametal layer. The layer 89 is an adhesive layer.

The layers 82, 83, 84, 85, 88 and 89 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 81 as described there.

The substitute layer 86 is formed by a transmissive material. Thatmaterial can also be the same material as the material used for thespacer layer 85. In that way, it is possible to forego partialapplication of the layers 85 and 86, as already described in thedescription relating to FIG. 5 a.

FIG. 6 b shows a carrier 91, seven layers 92, 93, 94, 95, 96, 98 and 99,diffractive structures 97 and a plurality of surface regions 99 athrough 99 d. The layer 92 is a protective lacquer and/or release layer.The layer 93 is a replication layer. The layer 94 is an absorptionlayer. The layer 96 is a substitute layer. The layer 98 is a metallayer. The layer 99 is an adhesive layer.

The layers 92, 93, 94, 95, 98 and 99 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 81, as described there. The substitute layer 96 is of theconfiguration as stated in relation to FIG. 6 a.

Prior to application of the layer 94 and/or the layer 96, thediffractive structures 97 are applied to the surface of the layer 93 bymeans of an embossing tool or one of the other above-describedprocesses. As can be seen from FIG. 6 b, in this case the diffractivestructures 97 can be applied both in surface regions which are coveredby the partial thin film element and also can be applied to thosesurface regions which are not covered by a partial thin film element.

FIGS. 7 and 8 show some possible ways of combining a partial thin filmelement with partial diffractive structures and partial metallisation.

FIG. 7 shows a carrier 101, nine layers 102 through 109 and a pluralityof surface regions 109 a through 109 d. The layer 102 is a protectivelacquer and/or release layer. The layer 103 is a replication layer. Thelayer 104 is an absorption layer. The layers 106, 107 and 107 a aresubstitute layers. The layer 108 is a metal layer. The layer 109 is anadhesive layer.

The layers 102, 103, 104, 105, 108 and 109 are of the configuration asdescribed with reference to FIGS. 3 and 4 and are applied to the carrier101 as described there.

The substitute layer 107 is a metal layer which can be constructed asdescribed in the embodiments shown in FIGS. 5 a and 5 b. The substitutelayers 106 and 107 a are formed by a transmissive material. They are ofthe structure as described in the embodiments illustrated in FIGS. 6 aand 6 b.

As can be seen from FIG. 7 a diffractive structure is further applied tothe layer 103 in the surface regions 109 b, 109 d and 109 e.

FIG. 8 shows a carrier 111, eight layers 112 through 119 and a pluralityof surface regions 119 a and 119 b. The layer 112 is a protectivelacquer and/or release layer. The layer 113 is a replication layer. Thelayer 114 is an absorption layer. The layer 117 is a spacer layer. Thelayers 116 and 115 are substitute layers. The layer 118 is a metallayer. The layer 119 is an adhesive layer.

The layers 112, 113, 114, 117, 118 and 119 are of the configuration asdescribed in the embodiments shown in FIGS. 3 and 4 and are applied tothe carrier 111 as described there.

The substitute layer 115 is a metal layer which can be of theconfiguration as described in the embodiments shown in FIGS. 5 a and 5b. The substitute layer 116 is formed by an etching resist (see also thedescription relating to the embodiment of FIG. 3).

As can be seen from FIG. 8 a diffractive structure 115 a and 114 arespectively is further applied to the layer 113 in the surface regions119 c and 119 d.

The above-described possible processes make it possible to producesuitably adapted individual elements such as a partial thin filmelement, a partial structuring (for example diffractive structures), apartial metallisation and a partial transparent window in a degree ofpositioning accuracy of 0.2 mm in any positional combination in the formof a continuous or extensive image pattern.

1. An optically variable element comprising a thin film in the form of apartial thin film element for producing color change by means ofinterference, and a further layer comprising a surface region, whereinthe partial thin film element comprises a surface region and wherein thepartial thin film element covers the surface region of the further layerin a region-wise and pattern-shaped manner.
 2. An optically variableelement as set forth in claim 1, wherein the partial thin film elementhas further comprises an absorption layer and a spacer layer.
 3. Anoptically variable element as set forth in claim 1, wherein the partialthin film element has further comprises a plurality of layers ofdifferent refraction.
 4. An optically variable element as set forth inclaim 1, wherein the partial thin film element further comprises areflective layer, preferably a metal layer.
 5. An optically variableelement as set forth in claim 1, wherein the partial thin film elementfurther comprises a diffractive structure for producing diffractioneffects.
 6. An optically variable element as set forth in claim 1,wherein the partial thin film element further comprises a partialreflective layer, in particular a metal layer, which partially coversthe surface region of the partial thin film element.
 7. An opticallyvariable element as set forth in claim 1, wherein the partial thin filmelement further comprises a partial diffractive structure for producingdiffraction effects, which partially covers the surface region of thepartial thin film element.
 8. An optically variable element as set forthin claim 1, wherein the surface region of the further layer, which isdelimited by the partial thin film element, comprises an absorptionlayer.
 9. An optically variable element as set forth in claim 1, whereinthe surface region of the further layer, which is delimited by thepartial thin film element, comprises a spacer layer.
 10. An opticallyvariable element as set forth in claim 1, wherein the surface region ofthe further layer, which is delimited by the partial thin film element,comprises one or more substitute layers which replace the thin filmlayer succession of the partial thin film element in said surface regionof the further layer.
 11. An optically variable element as set forth inclaim 10, wherein the surface region of the further layer delimited bythe partial thin film element is enclosed by the partial thin filmelement or encloses the partial thin film element.
 12. An opticallyvariable element as set forth in claim 10, wherein the one or moresubstitute layers have an overall layer thickness which approximatelycorresponds to the layer thickness of the partial thin film element. 13.An optically variable element as set forth in claim 10, wherein at leastone of the one or more substitute layers comprises a diffractivestructure for producing diffraction effects.
 14. An optically variableelement as set forth in claim 10, wherein the one or more substitutelayers comprise a reflection layer, in particular a metal layer, and acarrier layer.
 15. An optically variable element as set forth in claim10, wherein the one or more substitute layers comprises a singlereflection layer, in particular a metal layer.
 16. An optically variableelement as set forth in claim 10, wherein the one or more substitutelayers are transparent layers.
 17. An optically variable element as setforth in claim 10 wherein at least one of the one or more substitutelayers comprises a surface region and a partial reflective layer, inparticular a metal layer, which partially covers the surface region ofthe at least one of the one or more substitute layers.
 18. An opticallyvariable element as set forth in claim 10, wherein at least one of theone or more substitute layers comprises a surface region and a partialdiffractive structure, for producing diffraction effects, whichpartially covers the surface region of the at least one of the one ormore substitute layers.
 19. An optically variable element as set forthin claim 1, wherein the further layer is a full-area transparent layer,in particular a protective lacquer layer.
 20. An optically variableelement as set forth in claim 1, wherein the further layer is afull-area reflection layer, in particular a metal layer.
 21. Anoptically variable element as set forth in claim 1, wherein the furtherlayer is a full-area adhesive layer.
 22. A security product having anoptically variable element as set forth in claim
 1. 23. A foil, inparticular an embossing foil or a laminating foil, comprising anoptically variable element as set forth in claim 1.